Effects of Service Time on Mechanical Properties of Spiral Weld of Oil Pipelines

In order to study the effects of service time on mechanical properties of spiral weld of oil pipelines,a series of tensile and fatigue tests were performed on 16Mn oil pipeline materials,which were cut from the Luning oil pipeline with service for about 30 years and from a new pipeline.The results showed that tensile properties of 16Mn spiral weld pipeline material were stable and no distinct degradation was detected after long-time service.However fatigue properties of the pipeline materials with spiral weld were greatly reduced after long-term service and those without spiral weld had no obvious change.